"04 005 Porcelain veneers Part II"
Naval Postgraduate Dental School Clinical Update National Naval Dental Center 8901 Wisconsin Ave Bethesda, Maryland 20889-5602 Vol. 26, No. 5 May 2004 Porcelain veneers – part II: preparation and delivery Lieutenant Yaohsien Peng, DC, USNR, Captain Blaine Cook, DC, USN, and Captain Dean Beatty, DC, USN Introduction Porcelain Veneers Part I, July 2003, reviewed the evaluation and In preparing diastema closure, the interproximal preparation is treatment planning phases of porcelain veneer restorations. Part II extended through the contact toward the lingual. The greater will address clinical techniques used in tooth preparation, delivery, the space to be closed, the farther the preparation must be and the post-operative phases of treatment. carried to the lingual. It is also important to extend the interproximal preparation subgingivally to recontour the Traditional preparation design papilla. This type of preparation must be provisionalized to Traditional veneer preparation is a conservative reduction of tooth reduce sensitivity and prevent migration (1). structure consisting of 0.5mm facial reduction with interproximal finish lines facial to the contact area. Because all prepared surfaces Material options are generally in enamel and contacts are left undisturbed, the need Feldspathic porcelain. Traditionally, ceramic veneers are for temporization is minimized and the potential for pulpal fabricated by layering feldspathic porcelain onto a refractory involvement is significantly reduced. Supragingival veneer margins die or platinum foil (3). avoid the risk of irritation to periodontal tissues (1). Densely sintered high-purity magnesium oxide base coping, e.g. In-Ceram Spinell. The core is more translucent than the Preparation Procedure: traditional In-Ceram but does not posses the same flexure 1. Retract gingival tissue if necessary. strength. It can be veneered with feldspathic porcelain but is 2. Make a series of facial depth cuts by either using round carbide not necessary. burs, or BrasselerTM or NixonTM depth cutters. Reduction of 0.5 Heat-pressed ceramic material, e.g. IPS Empress. Leucite- mm is usually adequate and should follow the anatomic reinforced feldspathic porcelain has improved flexural strength, contours of the teeth. fracture resistance, and excellent marginal adaptation. It can 3. Place a “long chamfer” margin with an obtuse cavosurface also be veneered with feldspathic porcelain. angle, which exposes the enamel prism ends at the margin for better etching. The margin should closely follow the gingival Veneer delivery procedures crest. Preliminary inspection 4. Place the preparation margin labial to the proximal contact area Examine veneers under magnification. to preserve it in enamel. Check fit of veneers on dies by first trying veneers one-at-a- 5. Do not reduce the incisal edge if possible; this helps support the time and then all together. porcelain and makes chipping less likely. If the incisal length is Clean the restorations thoroughly in water with ultrasonic to be increased, the tooth should be reduced to allow for a agitation. minimum of 1.5mm of porcelain. Tooth Preparation 6. Avoid undercuts and visualize the path of insertion because an Thoroughly clean the preparations, making sure all provisional undercut will prevent placement of the veneer. luting agents are removed. 7. Connect depth cuts and margins. To prevent areas of stress Try-in restorations with water, first one-at-a-time and then all concentration in the porcelain, ensure the tooth preparation is together. Verify fit, shade, and insertion sequence. free of sharp angles. All prepared surfaces should be rounded Color Check and Characterization and smoothly flowing. Place one laminate in position with water or glycerine and then compare it to the shade tab selected. If the laminate appears Alternate preparation designs dark, then a lighter colored resin cement should be selected. Ultraconservative preparation design is more conservative than Utilize color-keyed try-in pastes to evaluate and select the the traditional veneer preparation, which can result in dentin appropriate shade (4). exposure in the cervical areas. This preparation design Veneers can also be characterized externally using a special advocates cervical reduction of 0.3mm and midfacial reduction laminate low-fusing color system, which fuses at approximately of 0.3mm to 0.5mm, which takes into account the mean thick- 1,400F. The laminate can also be supported with an instant ness of enamel (2). investment, which when set facilitates coloring and glazing with Extending traditional veneer preparation is appropriate for any conventional system (4). situations requiring hidden margins, or increased retention. In Cementation this design, proximal margins are extended into or through the Use rubber dam isolation or displacement cord, cotton rolls, contacts and the gingival margins are placed slightly and cheek retractors. subgingival. It is indicated for malaligned teeth, discoloration, Clean the teeth with pumice. Wash and dry. black space closure, veneers adjacent to crowns, replacing restoration or wrapping an existing restoration, and diastema closure (1). 35 Check with the dental laboratory to see if the fabricated veneers There is also an increase in papillary bleeding on probing in were etched. If not, etch the internal surface of the veneer with 25% of restored teeth with subgingival restoration margins (7). hydrofluoric acid for 5 minutes. Rinse and dry. Subgingivally placed margins of dental restorations are Silane is painted onto the etched porcelain to enhance the associated with pathologic alteration of the adjacent gingiva; adhesive properties of the resin. Allow to dry for one minute the greater the marginal inaccuracy of the restoration, the and gently air-dry the veneer surface (4, 5). greater the permanent damage to the periodontal tissue (7). Place a Mylar matrix strip, dead soft metal matrix, or plumber’s teflon tape interproximally to protect adjacent teeth. Maintenance Etch the enamel with 37% phosphoric acid for 30 seconds. Resin polymerization takes at least 72 hours to complete. Rinse thoroughly and dry. During this early phase, hard and extremely hot or cold food, Following the manufacturer’s instructions for cementing alcohol and medicated mouthwashes should be avoided. (4) veneers, apply bonding agent to etched enamel and etched, Patients will have a period of adjustment for the first two weeks silanated veneer surface but do not light cure. as they get used to the "new" teeth that changed in size and Apply light cure composite resin luting agent to the restoration. shape. Be careful to avoid trapping air. Patients should be instructed to use a soft toothbrush with Position the restoration gently, seating veneer from incisal to rounded bristles, and to floss daily. gingival. Remove excess luting agent with an instrument. Patients should also avoid biting on hard objects/food with Hold the restoration in place while light-curing the resin. Do restored teeth. not press on the center of veneers; they may flex and break. Routine cleanings are recommended at least every four months Remove excess cement before full cure being careful not to pull with a hygienist. Ultrasonic scalers and air abrasion systems cement out from veneer margin leaving a defect. should be avoided. Light cure for 40 seconds from several directions for 2-3 A hard night guard is useful to decrease the potential for minutes cumulative cure time per veneer. fracture of the laminate and excessive wear of the opposing Finishing arch. A soft acrylic mouth guard should be used for any form Remove resin flash with a scalpel or sharp curette. of contact sports. It is important to realize that the unsupported porcelain veneer should never be contoured until bonding is completed. References Finish accessible margins and occlusion with fine diamonds, 1. Rouse JS. Full veneer versus traditional veneer preparation: a using water spray. Use finishing strips for the interproximal discussion of interproximal extension. J Prosthet Dent. 1997 Dec; margins. 78(6): 545-9. Polish adjusted areas with an intra-oral porcelain polishing 2. Rouse J, McGowan S. Restoration of the anterior maxilla with system (rubber wheels or points, diamond polishing paste, etc.) ultraconservative veneers: clinical and laboratory considerations. Caution: for pressable systems, e.g. Empress, the color is on Pract Periodontics Aesthet Dent. 1999 Apr;11(3):333-9. the surface and can be polished away. 3. Zhang F, Heydecke G, Razzoog ME. Double-layer porcelain veneers: effect of layering on resulting veneer color. J Prosthet Seating sequence in multi-unit case Dent. 2000 Oct;84(4):425-31. Start with the two central incisors. It is essential that the veneers of 4. Garber DA, Goldstein RE, Feinman RA. Porcelain Laminate the central incisors be positioned correctly. The two lateral incisors Veneers. Quintessence Publishing Co. 1988: 90-98. are then seated, one at a time, to accommodate any discrepancies in 5. Kamada K, Yoshida K, Atsuta M. Effect of ceramic surface overall fit (4). There are numerous opinions about the cementation treatments on the bond of four resin luting agents to a ceramic sequence of the remaining veneers. Minor adjustments made on material. J Prosthet Dent. 1998 May;79(5):508-13. posterior teeth can be accomplished without jeopardizing esthetics. 6. Dumfahrt H, Schaffer H. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service: Part II- Factors influencing veneer failure Clinical results. Int J Prosthodont. 2000 Jan-Feb;13(1):9-18. Adhesion of the veneer seems to be the most important factor to 7. Christgau M, Friedl KH, Schmalz G, Resch U. Marginal reduce the compressive and tensile stresses in the veneer. adaptation of heat-pressed glass-ceramic veneers to dentin in vitro. Contamination during bonding significantly decreases the bond Oper Dent. 1999 May-Jun;24(3):137-46. strength of the porcelain veneers. LT Peng is a third year resident in the Prosthodontics Department. Higher porcelain veneer failure rates have been observed when Captain Cook is the Chairman of the Operative Dentistry the gingival margin is located on dentin. Today's dentin Department and Captain Beatty is a faculty member in the bonding agents are improved over previous generations but no Prosthodontics Department at the Naval Postgraduate Dental long-term data exist indicating the expected longevity of School. bonded dentin margins (6). Ideally all veneer margins should be on enamel. When cervical margins must be on dentin, The opinions and assertions contained in this article are the private utilize highly filled, viscous resin cements and dentin bonding ones of the authors and are not to be construed as official or agents of the latest generation to achieve greatest longevity (6). reflecting the views of the Department of the Navy. Patients who smoke increase their risk of veneer failure due to staining at the veneer margins (6). Note: The mention of any brand names in this Clinical Update does There is an increase in gingival recession in 31% of the not imply recommendation or endorsement by the Department of the patients, which ranged from 0.1 to 0.5mm. 88% of the Navy, Department of Defense, or the U.S. Government. recession is localized in teeth where the margin is subgingival. 36